Abstract
Purpose: :
Posterior capsule opacification (PCO) degrades visual function not only by reducing visual acuity, but also by increasing intraocular light-scatter. We used an in-vitro model to elucidate the effect of PCO-morphology on light-scatter and the functional aspect of light-scatter, as can be measured in the clinical setting by means of straylight.
Methods: :
Capsular bags were isolated from pseudophakic human donor bulbi. Using a goniometer setup and a camera, forward PCO-scatter was recorded. The camera position mimicked the anatomical position of the retinal photoreceptors; the camera recorded the scattered light that the photoreceptors would sense in an in-vivo situation. Scattered light was recorded at different wavelengths and scatter-angles (θ> 1°), which were divided into a near (θ≤ 7°) and far (θ> 7°) large-angle domain. The camera used the scattered light to produce grayscale images of PCO. Scatter intensities were interpreted in terms of straylight and compared to the straylight part of the point-spread function of the normal eye.
Results: :
Depending on morphology and severity, PCO-scatter could differ considerably in intensity. The scatter-intensity of PCO and the normal eye can also differ substantially, whereas their angular dependence is approximately the same. PCO-scatter shows the type of wavelength dependence that is normal for small particles: monotonically decreasing with increasing wavelength. These similarities changed somewhat at the near large-angle domain, where the angular and wavelength characteristics of PCO-scatter differed slightly from those of the normal eye.
Conclusions: :
Surprisingly, the angular dependence of PCO-scatter is comparable to that of the normal eye, suggesting similar underlying scattering processes. The data demonstrate that, apart from scatter, PCO has a refractile component, which dominates at the near large-angle domain and is most pronounced in pearl-type PCO.
Keywords: posterior capsular opacification (PCO) • optical properties • imaging/image analysis: clinical